Method for cementing well casings



Feb. 8, 1938. T. A. cRElGHToN METHOD FOR CEMENTING WELL CASINGS FiledOct. l, 1957 illllllL PatentediFeb. s, 1938 UNITED STATES PATENT OFFICEThomas A. Creighton, Long Beach, Calif., as-

signor of one-half to Jesse C. Wright, Los

Angeles, Calif.

Application October 1, 1937, Serial No. 166,790

9 Claims.

This invention relates to a method useful in well drilling operationsand relates more particularly to a method for cementing casing in aWell. A general object of this invention is to provide a simple, rapidand commercially practical method for cementing casing in a well.

In the drilling of deep wells such as oil wells, gas wells, etc. it isusually necessary to line or case the well with a casing to support thewall of the well and to exclude unwanted fluids from the well. It is thecommon practice to cement the lower portion of the casing in the well toprevent the contamination of the fluid to be produced and to preventboth the upward and downr ward passage of uid around the set casing. In

the methods now usually employed to cement a casing in a well the casingis run into the well to its nal position and cement is then pumped downthrough the casing,or through a tube within the casing, to the bottom ofthe well and is forced up around the lower portion of the casing by thepump pressure. In the rotary method of well drilling the well and thecasing are filled with the mud-laden drilling fluid and the cement iscontaminated with this drilling fluid when it is pumped through thecasing and forced up around the lower end of the casing. As the cementis forced up around the lower end of the casing it mixes with the mud onthe casing and on the Wall of the Well and follows the paths of leastresistance leaving channels or spaces occupied by mud and other foreignmaterial. This so-called channeling of the cement that encases the lowerportion of the casing often results in the leakage of water or otherunwanted fluid into the well and necessitates expensive and'timeconsuming operations to stop. the leakage around the casing.

Another object of this invention is to provide a method for cementing acasing in a well that assures a full and eiective shut-off around thecasing.

Another object of this invention is to provide a method for cementingwell casing that avoids the a method for cementing a'well casing inwhich it is unnecessary to pump the cement up around the casing shoewhereby the cement is free to flow at a slower rate and to completelyoccupy the annular space around the casing to form a tight, effectiveshut-off.

A further object of this invention is to provide a method for cementingwell casing that is easy to perform and that does not necessitate theemployment of expensive equipment.

The various objects and features of my invention will be fullyunderstood from the following detailed description of a typicalpreferred manner of carrying out the method of the invention, throughoutwhich description reference is made to the accompanying drawing, inwhich:

Fig. 1 is a longitudinal sectional view of the lower portion of a wellillustrating the cement being delivered to the well in accordance withthe method of the invention. Fig. 2 is a view similar to Fig. 1 showingthe casing about to enter the cement and Fig. 3 is a view similar toFig. 1 with the lower portion of the casing in vertical cross sectionand showing the casing set in the cement.

In the drawing I have illustrated the open or uncased lower portion of atypical well W. It will be assumed that the well is being drilled by therotary method and is iilled with the rotary mud M usually employed inthe rotary method of drilling. As illustrated in Fig. 1 of the drawing astring of drill pipe P is in the well W and carries at its lower end adrilling tool T. The tool T may have drilled the well W to the desireddepth. In accordance with the usual practice the well drilling tool 'I'has circulation ports I0 for discharging the drilling fluid or rotarymud M.

The method provided by the present invention includes, generally, thepassage or delivery of the proper amount of cement Il to the lowerportion of the well W through the drill pipe P, the removal of the drillpipe P and the tool T from the Well, providing a casing C having aclosure or a valved shoe S on its lower end and having a suitable floatvalve V, and then running the casing C into the well W to its finalposition in the well to displace the cement Il upwardly around its lowerend wherebyv the lower portion of the casing is embedded in the cement.

In accordance with the present invention the drill pipe P may be.employed to deliver or conduct the cement mixture or cement slurry tothe bottom of the well W. When the well W has been drilled to thedesired depth and while the drill pipe P remains in the well bore thecement Il may be passed down through the pipe. In practice the cementslurry Il is pumped Vthrough the drill pipe P by suitable pumpingequipment. The cement I l discharges from the ports I0 of the drillingtool T toow into the lower portion of the well. Thus the cement Il, inthe quantity previously determined, is delivered to the bottom of ,thewell bore W with little or no contamination. The drill pipe P conductingthe cement II of course prevents the mud M in the well W fromcontaminating the cement II las it is delivered downwardly into thewell.

The character of the cement I I delivered to the lower portion of thewell W is of particular importance to the method of the invention. Inaccordance with the invention Portland cement is employed that isretarded to attain its initial set in from 30 to 40 hours after mixing.When the required quantity of cement I I has been pumped into the'well Wthrough the drill pipe P the drill pipe carrying the tool T is withdrawnfrom the well. It is to be particularly noted that the cement II isdelivered to the lower portion of the well W in anuncontaminated statewithout the necessity of runninga special cementing string into thewell. As .the drill pipe P is already in the well at the start of thecementing operation Vthe employment of the pipe P to conduct the cementeffects a marked saving in time.

Immediately following the withdrawal of the drill pipe P and the tool Tfrom the well the casing C is assembled and run into the well. The shoeS on the lower end of the casing C is provided with means for preventingthe entrance of uid into the casing when the same is run into 4the well,whereby the casing C may be iloated into the well. In the particularcase illustrated in the drawing the shoe S has a cage I2 provided with avalve seat I3 and a ball valve I4 cooperates with the seat I3 to closethe lower end of the casing C. The valve V may be provided in the casingC to assure that the casing may be floated into the well in the eventthe valved shoe S leaks. The float valve V may be' of typicalconstruction and is designed to positively prevent up-ow in the casing Cand to trap or support a substantial head of fluid in the casing. 'I'hevalve V may be mounted or arranged in one of the couplings I5 of thecasing and may be provided at any desired point in the lower portion ofthe casing. The valve elements I2, I3 and I4 of the casing shoe S andthe iloat valve V are formed of frangible or drlllable material so thatthey may be readily drilled out when the well is to be completed ordeepened. The valve V may be of any typical construction and anysuitable form of valved shoe S or closure may bel employed on the lowerend of the casing C. Accordingly, the invention is not to be consideredas restricted to the use of the particular/vw 'structures illustrated inthe drawimg.

The casing C equipped with the valved shoe S and the iloat valve V, asdescribed above, is run into the well W in the usual manner. The valvedshoe S and the valve V positively prevent the up-flow of fluid in thecasing C and permit the casing to be floated vinto a deep well withoutdanger o1' parting through its own Weight. In floating the casing C intothe well W the valve V and the valved shoe S prevent the entrance of themud M tothe casing so that the hollow or empty casing has sutllcientbuoyancy to support itself against parting. It may be necessary to pourmud or other iluid F into the empty casing C to give it sufcient weightso that it may be run into the well. The casing C may be run through thewell to its final position.

During the latter portion of the downward movement of the casing C intothe well W the shoe S and the lower portion of the casing enters thecement Il. As described above, the cement II is retarded so that itremains in a fluid or plastic state until the casing C is embeddedin\-it. The valve I4 in the shoe S prevents the cement II from enteringthe casing C so that the casing displaces the cement II upwardly intothe annular space X between the casing and the wall of the well W.During the-passage of the casing C into or through the cement II it ispreferred to lower the casing C slowly so that the cement is made toslowly move upwardly around the casing C ln the space X as it isdisplaced by the slow moving casing. It is believed that it will bereadily understood how the casing C provided with the valved shoe Sdisplaces the cement I I to iiow upwardly in thespace X around thecasing.

When the casing C is in its nal position in the well the cement II isallowed to set and the cementing operation is complete. It is to beunderstood that the valve V, the valve elements I2, I3 and I4 in theshoe S, and any other internal parts of the shoe S may be removed orbroken out to permit the testing of the cement seal and the casing C andto permit completion of deepening of the well.

The method provided by the present invention for cementing well casingprevents channeling of the cement due to pumping of the cement upwardlyaround the lower end of the casing and thus assures an eiective iluidtight seal. The method may be readily carried out without employingspecial packers, etc. The cement II is delivered to the lower portion ofthe well W through the drill pipe P so that it is not contaminated bythe mud or iluid M in the well. The lowering of the casing C into themix or body of plastic cement II in the bottom of the well bore Wassures the complete embedding of the lower portion of the casing C inthe cement so that uid cannot possibly leak or ilow through the annularspace X between the casing and the wall of the well.

Having described only a typical preferred manner of carrying out themethod of my invention, I do not wish to be limited or restricted to thespecic details herein set forth, but wish to reserve to myself anyvariations or modifications that may appear to those skilled in the artor fall within the scope of the following claims:

Having described my invention, I claim:

1. The method of cementing a casing in a well comprising, depositing abody of plastic cement in the well, and then running the casing into thewell to enter it in the cement.

2. 'I'he method of cementing a casing in a well comprising passing abody of plastic cement to the lower portion of the well, providing thecasing with a. closure at its lower end, and running the casing into thewell to immerse its lower portion in the plastic cement.

`3. 'I'he herein described method comprising depositing a body ofplastic cement in a well by passing the cement down through a tubulardrilling string in the well, removing the drilling string from the well,running a casing into the well to introduce its lower end into thecement, and then allowing the cement to set.

4. The well drilling method comprising operating a tubular well drillingstring in a well, passing plastic cement through the string to the lowerportion of the well to occupy the same, removing the drilling stringfrom the well, lowering a well casing into the well to introduce thecasing into the cement and cause the upward dising a casing with aclosed lower end, running the placement of the cement around the casing,and then allowing the cement to set.

5. The well drilling method comprising operating a tubular well drillingstring in a well, passing plastic cement through the string to the'lower portion of the Well to occupy the same, removing the drillingstring from the well, lowering a casing having a closed lower end intothe well to enter its lower portion in the cement and thereby cause theupward displacement of the cement around the casing, and then permittingthe cement to set.

6. The method of cementing a. casing in a well comprising delivering amass o! plastic cement to the lower portion of the well, providing acasing with a valved lower end, running the casing into the well so thatits lower portion enters the cement and 'displaces the cement upwardlyaround the casing, and then allowing the cement to set.

7. The method of cementing 'a casing in a well comprising delivering amass of retarded plastic cement to the lower portion of thewell,providcasing into the well so that its lower portion enters the cementanddisplaces the cement upwardly around the casing, and then allowingthe cement to set.

8. The method of cementing a casing in a well comprising, delivering amass of retarded plastic cement to the bottom of the well, oating acasing into the well to enter the cement and displace the cement upwardaround the casing and then allowing the cement to set.

'9. The well drilling method comprising oper- `atinga tubular welldrilling string in a well, passing retarded plastic cement through thestring to the lower part of the well, removing the drilling string fromthe well, providing a casing with a valved shoe on its lower end,floating the casing into the well sov that its lower portion enters thecement and displaces the cement upwardly around the casing, lowering thecasing to its final position in the well, and then allowing the cementto harden.

THOMAS A. CREIGHTON.

